| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 21.9 | 122 |
| 2015 | 22.3 | 120 |
| 2014 | 22.7 | 120 |
| 2013 | 23.2 | 118 |
| 2012 | 23.7 | 115 |
| 2011 | 24.1 | 116 |
| 2010 | 24.6 | 115 |
| 2009 | 25.1 | 115 |
| 2008 | 25.7 | 114 |
| 2007 | 26.2 | 115 |
| 2006 | 26.7 | 115 |
| 2005 | 27.4 | 116 |
| 2004 | 28.1 | 114 |
| 2003 | 28.8 | 114 |
| 2002 | 29.5 | 113 |
| 2001 | 30.1 | 113 |
| 2000 | 30.7 | 110 |
| 1999 | 31.4 | 110 |
| 1998 | 32 | 110 |
| 1997 | 32.6 | 110 |
| 1996 | 33.1 | 110 |
| 1995 | 33.6 | 111 |
| 1994 | 34 | 110 |
| 1993 | 34.4 | 109 |
| 1992 | 34.7 | 109 |
| 1991 | 35 | 111 |
| 1990 | 35.1 | 112 |
| 1989 | 35.2 | 112 |
| 1988 | 35.2 | 115 |
| 1987 | 35.2 | 115 |
| 1986 | 35.2 | 115 |